Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
It is not clear from your description but if the expansion joint area is unenclosed and part of the ambient outside conditions (wind can blow through it) than I think it should be treated as an exterior surface and insulated following the nonresidential requirements on the admin block and the residential requirements on the housing block. This also applies if the space is more like a ventilated crawlspace area.
If on the other hand the space between the two blocks is fully enclosed but just not conditioned, it would be treated as semi-exterior envelope and then you would use the semi-heated requirements.
Unless the expansion joint area is fully enclosed and conditioned (which seems very unlikely) it will need some insulation based on 90.1.
Figure 5.5.2 from 90.1-2013 can help understand the interpretation.
Please note this is just my personal unofficial interpretation and only represents my viewpoint and should not be viewed as an official statement from ASHRAE.
